1. Field of the Invention
The present invention relates to an air-cooled type laser device having a laser diode as a light emitting source or an excitation light source, and having a structure to radiate heat generated from the laser diode.
2. Description of the Related Art
Generally, in a laser device, having a laser diodes (or semiconductor lasers) as a light emitting source or an excitation light source, there are two types, i.e., an air-cooled type in which heat generated by a laser diode module including a laser diode is radiated by air; and a water-cooled type which is connected to a circulation type cooling water supply device (or a chiller).
The air-cooled type laser device is more advantageous than the water-cooled type, in that the air-cooled type is easily moved, an occupied area thereof is small, restrictions of an installation location thereof are few, and an installation cost thereof is low, etc. However, in the air-cooled type, it is difficult to decrease the temperature of the laser diode module to the same degree of the water-cooled type. In particular, since a high-power laser device must have many laser diode modules having a large amount of heat generation, it is necessary to provide an effective heat radiating structure to the laser device in order to prevent the laser device from having to be increased in size.
As a relevant prior art document, JP 2008-021899 A discloses a laser oscillator having a semiconductor laser heat radiating member to radiate heat generated by a semiconductor laser array, a fiber laser heat radiating member to radiate heat generated by an optical fiber for a fiber laser, a cooling fan for sending cooling air, and a guide member for guiding the cooling air from the cooling fan.
JP 2012-059952 A discloses a structure for cooling an electronic device, including a heat radiator having an L-shaped heat pipe, a plurality of heat radiating fins attached to a substantially horizontal part of the heat pipe, and a heat receiving plate to which substantially vertical portions of the heat radiating fins are attached; a plurality of electronic devices attached to the heat receiving plate; and a container for containing the plurality of electronic devices.
JP 2009-239166 A discloses a flat heat sink including: a plurality of thin plates layered having an air guiding portion and a hollow portion for containing a centrifugal fan, the thin plated being layered with a certain gap therebetween; at least one heat radiating fin part connected to ends of the thin plates, in which air guided by the air guiding portion of the thin plates flows through the heat radiating fin part; and at least one heat pipe, having one end which is thermally connected to the portion of the thin plate thermally connected to a heating component and the other end which is thermally connected to the heat radiating fin part, in which at least a part of the heat pipe is positioned so as to form a space between the thin plates and the heat pipe.
Further, JP H09-326579 A discloses a cooling unit having a heat receiving part positioned on a heating element, a heat sink having a cooling fan, a plurality of heat transferring parts for transferring heat of the heat receiving part to the heat sink, and a connecting part positioned between the heat transferring parts so that the heat transferring part is detachable.
In many cases, an air-cooled laser device has a fin set including a plurality of fins positioned having a certain gap. In this regard, in order to improve cooling efficiency of the fin set, it is more effective to increase an area of an inlet portion (or an inlet area) for the cooling air defined by the fin set, than to increase a length of the heat radiating fin (or a fin length) along an air-flow direction. Further, it is preferable that a large amount of cooling air flow between the fins as possible, whereas the amount of cooling air is decreased when the fin length is long, since a pressure loss of the cooling air is increased.
In order to improve the cooling efficiency, it is preferable to use a heat radiating structure through which air can smoothly flow, in which the number of portions, where the flow direction of the air is changed (i.e., the pressure loss is increased), is reduced as possible. However, in many cases, the air-cooled laser device includes components such as a power-supply unit, etc., other than the laser diode module, and such components may also generate heat. Therefore, it is desired that the air smoothly flow without being blocked by the components, while cooling the components.
The above related art documents do not provide a sufficient solution for solving the above problems. For example, in a heat radiating structure as shown in FIG. 5 of JP 2008-021899 A, the flow of cooling air is changed by a substantially right angle so as to flow in the upward and downward directions, after the cooling air collides with a heat radiating fin for a semiconductor laser (or a laser diode module), and then, the flow of the cooling air flowing in the downward direction is changed again by a substantially right angle so that the cooling air flows to a heat radiating fin for a fiber laser. Therefore, the pressure loss of the cooling air may be relatively high. Further, since it could be understood that heat of heating components other than the semiconductor laser and the fiber laser is radiated by natural convection, a temperature rise of the heating components may affect reliability of the laser device.
As explained above, in a high-power air-cooled laser device having a laser diode as a light emitting source or an excitation light source, it is necessary to arrange components other than the plurality of laser diode modules, such as a power-supply unit and a control unit, in a housing of the laser device. The conventional laser unit does not have sufficient heat radiating performance, since a surface area for radiating heat from the heating components is limited and/or the cooling air cannot smoothly flow and the flow rate thereof is decreased, due to the existence of the heating components.